Rearend Measurements

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I am just finishing up a 9 inch swap and thought I would post some info for anyone doing the same.

I have a 72 swb with a 12 bolt and coil spring suspension.
64.5" Drum face to drum face for differential width
40" Trailing arms width apart.

On a stock 12 bolt the center of the perch is 8.5 inches from the backing plate at its most inboard edge. Since the brackets weld on at an angle using the center measurement can be a bit of a guess. If you measure again off the backing plate at it's most inboard edge the aft hole is 8 inches and the front hole is 9 inches from the backing plate to the centre of the hole.
My 9 inch came from a 79 bronco and to my surprise the inside backing plate to backing plate measurement is the same as my 12 bolt so it made the measuring easy. Remember I'm working off of the backing plate itself, not the backing plate flange.
Pinion Angle,
With the mounting perches completely level 0 degrees. The pinion points up and registers 76 degrees on my protractor. I take my measurements off the bottom of the perches and the face of the yoke with the bolts removed. I found this to be the easiest way to set the pinion angle rather than try to work with two measurements, you may have another way.
I couldn't find much in the way of measurements before I started so I hope this helps someone.